Evidence for early life (3.8 to 4.3 billion years ago) in Earth’s oldest hydrothermal vent precipatates

Although it is not known for certain when or where life on Earth began, many evolutionary biologists would agree that some of the earliest habitable environments most likely would have included oceanic hydrothermal vents. In the attached report, authors provide evidence of putative fossilized microorganisms that have been carbon-dated to at least 3,770 million years old –– and possibly 4,280 million years old. [Current estimates of the age of Earth are 4,543 million years.] These putative fossilized microorganisms existed in ferruginous sedimentary rocks, interpreted as seafloor hydrothermal vent-related precipitates, from the Nuvvuagittuq Belt in Quebec, Canada. These structures occur as micrometer-scale hematite tubes and filaments with morphologies and mineral assemblages similar to those of filamentous microorganisms from modern hydrothermal vent precipitates and analogous microfossils in younger rocks.

The Nuvvuagittuq rocks contain isotopically light carbon in carbonate and carbonaceous material, which occurs as graphitic inclusions in diagenetic carbonate rosettes, apatite blades intergrown among carbonate rosettes, and magnetite–hematite granules, and is associated with carbonate in direct contact with the putative microfossils. [“Diagenetic” describes the change of sediments or existing sedimentary rocks into a different sedimentary rock during and after rock formation (lithification), at temperatures and pressures less than that required for the formation of metamorphic rocks.]  Collectively, these observations are consistent with an oxidized biomass and provide evidence for biological activity in submarine-hydrothermal environments more than ~3.8 billion years ago.

Nature 2 Mar 2o17; 543: 60–64

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